1. Field of the Invention
The present invention relates generally to the field of insect dispensing, and more specifically to metered dispensing of sterile insects from refrigerated trays through an air-gathering acceleration chute.
2. Description of the Prior Art
It is well known that insects can injure people and destroy their food supplies. Some carry disease or venom toxic to man while others simply destroy livestock or corps. They have also been known to decimate the ranks of endangered animal and plant species valued by man. The cultivation of any animal or plant tends to support an increased population of its natural enemies. In early days, controlled fires were started to drive insects away with smoke and more recently a variety of insecticides such as DDT have been developed. The harmful legacy of these insect poisons is well known today, and the environment has only begun to recover in many areas.
In the aftermath of toxic insecticide damage, an alternative approach has been developed. Insects of any given problem-causing species are collected and bred in large numbers and then sterilized by exposure to certain wavelengths of electromagnetic radiation. The preferred part of the spectrum is x-rays. The sterilized insects are then dispersed into the general insect population over targeted areas. Vast numbers of fertile insects mate with the sterile insects, producing no offspring. As the number of offspring dwindles, so does the targeted insect population. This is an excellent approach because no poisons are released and the environment remains undamaged.
A problem with dispensing sterilized insects is that present dispensing procedures damage many of them, resulting in low efficiency and high cost. Sterile insects are typically carried over fields in airplanes and simply dumped out of cardboard boxes. The high impact of the passing air stuns and tears wings off a large percentage of these insects. Sporadic dumping from boxes also results in little or no uniformity of dispensing. As a result, many more insects must be bred, sterilized and dispensed than are actually needed for a given area.
There are a few aerial dispensing devices in related art which could be used to dispense live insects. Each of these devices has serious disadvantages, however, making them impractical.
The following are examples of such prior art devices.
Johnson U.S. Pat. No. 3,484,062, issued on Dec. 16, 1969, discloses an aerial dispensing apparatus for crop dusting. Powdered or granular material is retained in a hopper having downwardly convergent sidewalls. The material flows through the base of the hopper into rotors with radial blades which meter the flow. From the rotors the material drops into two main air ducts fed by a ram air scoop projecting beneath the fuselage. The air stream carries the material through delivery ducts in the wings and out of the plane through ejector tubes. Small air-gathering tubes referred to as "pick-up diffusers" are located periodically along the delivery ducts in the wings. These tubes inject small amounts of outside air into the ducts, their purpose being to create a swirling effect to diffuse the material throughout the air stream. The ram air design of Johnson causes abrupt acceleration, and when used for insect dispensing rather than crop dusting, the procedure results in insect damage and low efficiency as described above.
More recent and more similar in purpose is Maedgen, U.S. Pat. No. 4,260,108, issued Apr. 7, 1981. Maedgen is designed for dispersing insect eggs. Once again, a hopper having a conical lower portion is disclosed. A metering device is provided at the base of the hopper, taking the form of a perforated plate. This plate is rotated to present an opening of suitable size to permit a desired flow rate. A chute for gathering air and dispersing the eggs is attached beneath the plane. A problem with dispensing insect eggs is that large numbers of them are often destroyed by ants and other predators. A problem with dispensing live insects from Maedgen's chute is that the air stream within the chute which would receive the insects has a higher velocity than the air surrounding the plane. The resulting high air impact would enhance rather than reduce insect damage. Also, the depth to which the insects would have to be piled in the hopper to carry a full load would damage many of them.
Finally, Bjerregaard, U.S. Pat. No. 4,537,333, issued Aug. 27, 1985, is directed to a specific metering rotor arrangement for an airborne particle dispenser. The focus of Bjerregaard is the use of a plate mounted adjacent to the rotor blades to prevent clogging and crushing of particles. Bjerregaard presents no solution to the problems of insect damage caused by deep piling or high air impact.
It is therefore an object of the present invention to provide an insect dispenser which can carry a large quantity of insects without piling them more than two and one-half inches deep.
It is another object of the present invention to provide a dispenser which gently accelerates the insects to the speed of the air passing the delivery vehicle.
It is still another object of the present invention to provide a dispenser which dispenses insects at a constant rate for uniform distribution.
It is finally an object of the present invention to provide a dispenser which can safely and compactly store insects until they are dispensed.
A further object of the present invention is to provide a dispensing apparatus which increases, over the prior art, the efficiency of providing undamaged infertile insects at a ground location by means of an aircraft.